POS0416 DISTINCT DEGENERATION MECHANISMS IN INTERVERTEBRAL DISCS ADJACENT TO MODIC CHANGES
Authors: T. Mengis, I. Heggli, N. Herger, B. Aradi-Vegh, B. Roschitzki, J. Grossmann, F. Brunner, R. Marcus, M. Farshad, O. Distler, S. Dudli
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Modic changes (MC) are painful vertebral bone marrow lesions and are often found in patients with chronic low back pain. The adjacent intervertebral disc (IVD) seems to play an important role: the rapidly degrading disc stands in an inflammatory cross-talk with the MC bone marrow and MC develop almost always simultaneously cranial and caudal to a degenerated IVDs. Few studies have investigated expression of inflammatory cytokines and proteases expressed by IVD cells adjacent to MC, however, how this affects the ECM degeneration has not been determined. <h3>Objectives</h3> The aim of this study was to identify MC-specific mechanisms in degenerated discs. We hypothesize that the 'Modic discs' have a distinct disc matrix degradome. <h3>Methods</h3> Degenerated lumbar IVDs from MC1 (n=26), MC2 (n=20) and non-MC (n=19) levels from gender and age matched patients undergoing spinal fusion surgery were collected. Degradome was measured with N-terminal amine isotopic labeling of substrates (TAILS) liquid chromatography tandem mass spectrometry (LC-MS/MS). TAILS allows to identify degraded proteins by detecting de novo N-terminal peptides. Sequence motifs were calculated using TwoSample Logo web application to identify significantly enriched amino acids around the cleavage site of the top 50 upregulated peptides. Since proteases have preferences for amino acid sequences, different sequence motifs can indicate activity of different proteases. Proteases were matched to cleavage sites of the top 50 enriched MC1 and MC2 peptides using TopFINDer database. <h3>Results</h3> Mean degree of disc degeneration as measured by Pfirrmann grade was not significantly different between all groups (MC1: 3.8 ± 0.9, MC2: 4.2 ± 0.6, non-MC: 3.6 ± 0.8). A total of 487 (MC1), 419 (MC2), and 404 (non-MC) different protein fragments were detected of which 21.0%, 12.2% and 9.4% were unique to MC1, MC2, and non-MC, respectively (Figure 1a). Comparing MC1 to non-MC discs, the degradome was more complex with a variety of ECM fragments enriched (e.g. type II collagen, fibrinogen), while fragments of type I collagen, clusterin, and fibronectin were depleted (Figure 1b). In MC2 discs, mainly fibronectin and clusterin were enriched, while type I collagen was depleted (Figure 1b). Sequence motifs show unique cleavage preferences for each group (Figure 1c) indicating activity of different proteases in MC1 and MC2 discs. TopFinder identified neutrophil elastase as an important protease in all groups targeting cleavage of different proteins. In MC1 and MC2 IVDs kallikrein 3 as well as MMP9 and MMP2 are associated with found cleavage products. Finally, in MC1 TopFINDer uniquely identifies multiple fragments created by MMP2, MMP7, MMP12, MMP13 or cathepsin B. <h3>Conclusion</h3> MC1, MC2 and non-MC discs have different ECM degradomes that may be caused by the activity of different proteases. Differences in disc degeneration mechanisms and in the type and amount of bioactive ECM fragments explain why not all degenerating discs lead to adjacent MCs. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Tamara Mengis: None declared, Irina Heggli: None declared, Nick Herger: None declared, Borbala Aradi-Vegh: None declared, Bernd Roschitzki: None declared, Jonas Grossmann: None declared, Florian Brunner: None declared, Roy Marcus: None declared, Mazda Farshad: None declared, Oliver Distler Speakers bureau: Bayer, Boehringer Ingelheim, Janssen, Medscape, Consultant of: 4P-Pharma, Abbvie, Acceleron, Alcimed, Altavant Siences, Amgen, AnaMar, Arxx, AstraZeneca, Baecon, Blade, Bayer, Boehringer Ingelheim, Corbus, CSL Behring, Galapagos, Glenmark, Horizon, Inventiva, Kymera, Lupin, Miltenyi Biotec, Mitsubishi Tanabe, MSD, Novartis, Pfizer, Prometheus, Redxpharna, Roivant, Sanofi and Topadur, Grant/research support from: BI, Kymera, Mitsubishi Tanabe, Stefan Dudli: None declared.